Phase behavior of thin film Mn/GaAs interfacial reactions

摘要

Rutherford backscattered spectrometry, x-ray diffraction, and cross-sectional transmission electron microscopy were used to examine Mn/GaAs interfacial reactions. Mn films deposited in situ on molecular beam epitaxy (MBE)-grown GaAs(001) epilayers resulted in significant interfacial reactions following post-growth anneals above 200℃. These reactions initially resulted in the formation of a two-phase region of tetragonal Mn_2As and tetragonal δ-MnGa, with an average composition of Mn_(0.6)Ga_(0.2)As_(0.2), and were found to be limited by the rate of Mn diffusion through the reacted region. The two phases formed an epitaxial lamellar layer on the GaAs substrate with Mn_2As(001)< 100 > and δ-MnGa(001)< 100 >//GaAs(001)< 110 >. Higher temperature anneals resulted in the dissociation of the Mn_(0.6)Ga_(0.2)As_(0.2) region into a δ-MnGa layer near the sample surface and a Mn_2As layer near the GaAs substrate. Results of these reaction studies have been used to make predictions of the Mn-Ga-As ternary phase diagram for temperatures up to 400℃, which indicates that both Mn_2As and δ-MnGa are thermodynamically stable in contact with GaAs.